Group I p21-activated kinases in leukemia cell adhesion to fibronectin

Abstract

P21-activated kinases (PAK) regulate processes associated with cytoskeleton dynamics. PAK expression in leukemia cells was measured on protein and mRNA levels. In functional assays, we analyzed the effect of PAK inhibitors IPA-3 and FRAX597 on cell adhesivity and viability. PAK2 was dominant in cell lines, whereas primary cells also expressed comparable amount of PAK1 transcription isoforms: PAK1-full and PAK1Δ15. PAK1Δ15 and PAK2 levels correlated with surface density of integrins β1 and αVβ3. PAK1-full, but not PAK2, was present in membrane protrusions. IPA-3, which prevents PAK activation, induced cell contraction in semi-adherent HEL cells only. FRAX597, which inhibits PAK kinase activity, increased cell-surface contact area in all leukemia cells. Both inhibitors reduced the stability of cell attachment and induced cell death.

PAK1 and PAK2 in cell metabolism regulation

“…Accordingly, both the OCR and ECAR were markedly reduced by 20 µM IPA-3 in all leukemia cell lines tested (Fig. 3A), except for MOLM-7, which has a very low amount of PAK1 and a high PAK2 level (Kuželová et al, 2021). Increasing the IPA-3 dose to 50 µM was sufficient to achieve a marked decrease in the OCR and ECAR also in the latter cell line (data not shown).…”

“…An alternative PAK inhibitor, FRAX597, binds to the ATP-binding site of kinase-active PAK molecules and prevents PAK kinase activity but presumably does not directly interfere with nonkinase PAK functions (Licciulli et al, 2013). We have previously described the effects of these inhibitors on cell adhesion and viability in adherent HeLa and HEK293T human cancer cell lines (Grebenova et al, 2019) as well as in human leukemia cells (Kuželová et al, 2021). In the present work, we used PAK inhibitors at previously optimized concentrations regarding efficiency and toxicity: IPA-3 and PIR3.5 were added at 20 and 50 µM, and FRAX597 was added at 2 and 10 µM.…”

“…Leukemia cells are reportedly very sensitive to PAK inhibition (Kuzelova et al, 2014; Kuželová et al, 2021; Pandolfi et al, 2015), and treatment with IPA-3 induces cell death in the majority of leukemia cell lines. Accordingly, both the OCR and ECAR were markedly reduced by 20 µM IPA-3 in all leukemia cell lines tested (Fig.…”

“…Nevertheless, they interact with stromal cells, as well as with the extracellular matrix (ECM) of the bone marrow, and these interactions have a profound impact on their behavior. The adhesion structures of leukemia cells are more dynamic than those of adherent cells and they are usually not tightly connected to the actin cytoskeleton, but PAKs are still involved in the regulation of leukemia cell adhesion to the ECM (Kuželová et al, 2021). In addition, PAKs are indispensable for leukemia cell survival, as their inhibition leads to rapid cell death (Kuzelova, Grebenova, Holoubek, Roselova, & Obr, 2014; Kuželová et al, 2021; Pandolfi et al, 2015).…”

“…The adhesion structures of leukemia cells are more dynamic than those of adherent cells and they are usually not tightly connected to the actin cytoskeleton, but PAKs are still involved in the regulation of leukemia cell adhesion to the ECM (Kuželová et al, 2021). In addition, PAKs are indispensable for leukemia cell survival, as their inhibition leads to rapid cell death (Kuzelova, Grebenova, Holoubek, Roselova, & Obr, 2014; Kuželová et al, 2021; Pandolfi et al, 2015). Similar to solid tumors, leukemia cells often display a preference for aerobic glycolysis (Jiang & Nakada, 2016), and the metabolic phenotype has been proposed as a prognostic parameter for clinical outcome in acute myeloid leukemia (Chen, W. L. et al, 2014; Herst, Howman, Neeson, Berridge, & Ritchie, 2011).…”